Automated analyte supercritical fluid extraction apparatus

ABSTRACT

An apparatus for automated extraction of an analyte from a sample positioned in a sample containment cell having a fluid passageway structure for communication of an extraction fluid to and from the cavity of the cell. The apparatus includes a loading tray, an oven assembly mounted proximate the loading tray, a fluid communication assembly mounted proximate the tray, a cell manipulation assembly and a controller. The cell manipulation assembly brings an inlet conduit and an outlet conduit of the fluid communication assembly into sealed relationship with the sample containment cell and uses the conduits to pick up and move the cell to and from the cell tray and oven assembly. The fluid communication assembly further causes flow of an extraction fluid into the cell and pressurizes the cell for extraction of an analyte from the sample under elevated temperatures and pressures, which can be under supercritical conditions for supercritical fluid extraction but preferably are below supercritical conditions for solvent extraction. The apparatus and method include a solvent extraction soak, purging of the extracted fluid, flushing with a gas and rinsing so as to avoid contamination of subsequent analyte extractions.

RELATED APPLICATION

This application is a continuation-in-part application based uponco-pending parent application Ser. No. 08/259,667, filed Jun. 14, 1994for "Accelerated Solvent Extraction System."

TECHNICAL FIELD

The present invention relates, in general, to a method and apparatus forextracting analytes from a sample, and more particularly, relates to anapparatus and method for solvent extraction or supercritical fluidextraction of organic analytes from a solid matrix sample under elevatedtemperatures and pressures.

BACKGROUND ART

The extraction of various analytes from solid matrix samples using afluid under elevated temperatures and pressures sufficient to cause thefluid to be in a supercritical condition is well known and has been inuse for many years. Carbon dioxide, for example, is a commonly employedmaterial for supercritical analyte extraction. The carbon dioxide willbe held in a container or cell which is raised to a temperature andpressure which causes the carbon dioxide to operate as a supercriticalfluid. While in the supercritical conditions, the fluid is forcedthrough a porous sample to cause extraction of analytes from the sample.A wide range of samples and analytes are amenable to such supercriticalextraction techniques.

It also has been found that the addition of a solvent to a supercriticalfluid, in relatively low percentages, for example, 10% or less, willenhance the supercritical extraction process. While supercritical fluidextraction, with solvent augmentation, enhances the supercritical fluidextraction result, the temperatures and pressures at which the fluid ismaintained in supercritical condition are greater than would be optimumfor a pure solvent extraction.

Accordingly, it has been recently discovered that a highly effectivesolvent extraction process for the extraction of organic analytes from asolid matrix sample can be accomplished by maintaining an organicanalyte in contact with a non-aqueous organic solvent system in anextraction cell under temperatures of pressure below supercriticalconditions. This process is described in detail in commonly owned,parent U.S. patent application Ser. No. 08/259,667, filed Jun. 14, 1994,and entitled "Accelerated Solvent Extraction System," which applicationis incorporated herein by reference in its entirety.

While solvent extraction at elevated temperatures below supercriticalconditions has been found to be highly advantageous, it further ishighly desirable to provide a method and apparatus for automaticoperation of such a solvent extraction process. Moreover, forapplications in which supercritical fluid extraction has advantages overa solvent extraction process, it is desirable to have an apparatus andmethod for automating the supercritical fluid extraction process.

There are commercially available apparatus for automating thesupercritical fluid extraction process, but such systems have haddisadvantages in the cells employed, their sealing schemes and thephysical manipulation of cells and collection vials. Such apparatus dobroadly include, however, cell storage trays, oven assemblies,extraction fluid communication assemblies and devices for moving therespective components in an automated sequence.

Accordingly, it is an object of the present invention to provide amethod and apparatus which is suitable for automated analyte extractionusing a solvent extraction process or a supercritical fluid extractionprocess which employs enhanced component handling and cell sealingstructures that increase operational safety and reduce contaminationpotential.

Another object of the present invention is to provide an automatedanalyte extraction apparatus and method which allows high temperatureand high pressure extractions to be automatically accomplished rapidlyand with minimal technician supervision.

A further object of the present invention is to provide an automatedanalyte extraction system which is durable, low in cost, easy tomaintain, will accommodate samples of various size, and is suitable forsingle or multiple cycle extractions.

DISCLOSURE OF INVENTION

The automated extraction apparatus of the present invention is useful inimplementing either a solvent extraction process or a supercriticalfluid extraction process in which an analyte is removed from a sample,such as a solid matrix sample, positioned in the cavity of a samplecontainment cell.

In one aspect of the present invention the present apparatus iscomprised, briefly, of a loading tray formed for support of at least onecell, an oven assembly mounted proximate the tray and formed for heatingof the cell and a sample contained in the cell, a fluid communicationassembly mounted proximate the tray and including an inlet conduit andan outlet conduit formed for selective fluid coupling to a fluidpassageway structure in the cell for communication of an extractionfluid to and from the sample-containing cavity. The fluid communicationassembly is further formed to produce an elevated pressure of theextraction fluid while in the cavity of the cell. The apparatus furthercomprises a cell manipulation assembly mounted proximate the tray whichcarries the inlet and outlet conduit of the fluid communication assemblyand is formed to move the inlet and outlet conduit into engagement withthe cell to fluid couple the inlet conduit and the outlet conduit to thepassageway structure of the cell and to simultaneously thereby grip thecell between the inlet and outlet conduits. The cell manipulationassembly further is formed to move the cell as gripped by the inletconduit and the outlet conduit between the tray and the oven assembly,and the apparatus also includes a controller coupled to the cellmanipulation apparatus and the fluid communication apparatus for controlof fluid coupling and uncoupling with the cell, and for control ofmovement of the cell into and out of the oven assembly, and for controlof communication of extraction fluid to and from the sample, and forcontrol of the pressurization of the extraction fluid in the cavity.

In another aspect of the present invention, the present apparatuscomprises, briefly, a cell support structure, a sample containment cellmounted in the cell support structure and having a body defining asample-receiving cavity, a removable cap mounted to an access opening inthe body to the cavity, a passageway extending through the cap to thecavity for the flow of an extraction fluid through the cap to thecavity, a cap seal assembly positioned between the body and the cap toseal the cap to the body upon application of inward force to the cap anda passageway sealing assembly carried by the cell proximate thepassageway. A fluid communication assembly also is provided which ismounted proximate the cell support structure and formed for selectivefluid coupling to and uncoupling from the fluid passageway forcommunication of an extraction fluid to and from the cavity and forproducing an elevated pressure of the extraction fluid in the cavity.Finally, a manipulation assembly is mounted proximate the cell supportstructure and is formed to move a portion of the fluid communicationassembly into sealed relation with the passageway sealing assemblycarried by the cell for fluid coupling of the communication assembly tothe passageway, and in the preferred form the manipulation assembly alsourges a portion of the fluid communication assembly against the cap atapered surface on the cap to automatically align and stabilize the celland to apply an inward force to the cap to seal the cap against the cellbody. Also in a preferred form, the cell support structure can beprovided as an oven assembly including a clamping device formed inposition to apply clamping force to the cap so as to enhance sealing ofthe cap against the cell body.

In a further aspect of the present invention, a process for extractionof an analyte from a sample is provided which is comprised, briefly, ofthe steps of displacing a fluid conduit assembly into sealed engagementwith a passageway structure of a sample containment cell tosimultaneously align, seal and grip the cell in a stable manner with theconduit assembly; while gripping the cell with the conduit assembly,moving the cell between a storage tray and oven assembly; causing flowof an extraction fluid from an extraction fluid reservoir to the cavityin the cell through the conduit assembly; elevating the pressure of theextraction fluid while the extraction fluid is in the cavity; heatingthe extraction fluid while at an elevated pressure; and thereafterpurging the extraction fluid from the cavity through the conduitassembly to a fluid receptacle.

The process of the present invention also may be comprised of the stepsof displacing a fluid conduit assembly into sealed engagement with apassageway structure of a sample containment cell while causing flow ofan extraction fluid from a fluid reservoir to the cavity, elevating thepressure of the extraction fluid while in the cavity, and while theextraction fluid is at an elevated pressure, clamping a removableclosure member provided on the cell while heating the extraction fluidusing an oven assembly.

Finally, in a further aspect the process is comprised of the steps ofdisplacing a fluid conduit assembly in a sealed engagement with apassageway structure in a sample containment cell to simultaneously sealthe fluid conduit assembly to the cell and to seal a closure member forthe cell to the body of the cell with the conduit assembly.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic representation of a flow diagram for the apparatusand method of the present invention.

FIG. 2 is a top perspective view of an apparatus constructed inaccordance with the present invention with various components removedand the appearance panels removed for ease of illustration.

FIG. 3 is a top plan view, slightly enlarged, of the apparatus of FIG.2.

FIG. 4 is a top perspective view of a containment cell tray andmanipulation portion of apparatus of the present invention.

FIG. 5 is a top perspective view, somewhat enlarged, of an oven assemblyconstructed in accordance with the present invention.

FIG. 6A is a top perspective view of a cell manipulating arm assemblyshown in an extended position for gripping of a cell from the trayassembly of FIG. 4.

FIG. 6B is a top perspective view of the arm assembly of FIG. 6A shownin the retracted position.

FIG. 7 is a fragmentary, top plan view of the apparatus of FIG. 2 withthe cell manipulating carousel removed for illustration of the vialmanipulating carousel.

FIG. 8 is a top perspective view of the vial manipulating assemblyportion of the apparatus of FIG. 2.

FIGS. 9A, 9B and 9C are top perspective views of the outlet conduitmanipulating assembly shown in a fully retracted position, anintermediate position and a position for deposit of fluid into acollection vial, respectively.

FIG. 10 is a side elevation view, in cross section, of a samplecontainment cell for use with the apparatus and process of thepresent-invention, showing also a portion of the oven assembly.

BEST MODE OF CARRYING OUT THE INVENTION

The method and apparatus of the present invention are particularly wellsuited for implementing rapid analyte extractions by using solvents athigher temperatures than conventional solvent extraction techniques andunder pressures which, when combined with the elevated temperatures, arelower than supercritical conditions. The advantages of such solventextractions are set forth in co-pending, parent U.S. patent applicationSer. No. 08/259,667 and will not be repeated herein. The apparatus ofthe present invention is particularly well suited and designed for usewith the elevated temperature and pressure solvent extraction method ofthe co-pending application, but it also may be used, or adapted for use,with conventional supercritical fluid extraction processes.

Referring now to FIG. 1, a flow diagram of the present apparatus isshown. The automated extraction apparatus, generally designated 21, isdesigned for use with a sample containment cell, generally designated22, and shown in more detail in FIG. 10. The details of construction ofcell 22 will be described only briefly in this application but are thesubject of a commonly owned United States Patent application filedcontemporaneously with this application and also incorporated herein byreference.

Automated extraction apparatus 21 further preferably includes a cellsupport structure or cell tray 23, in which cells can be stored orloaded for automatic handling. In some embodiments of the presentinvention, however, cell-tray 23 is optional. Similarly, it ispreferable that solvent extraction occur at elevated temperatures, andit is necessary that supercritical fluid extraction occur at elevatedtemperatures. Accordingly, the present apparatus preferably includes anoven assembly, generally designated 24, which is mounted proximate tray23 and is formed for heating of cell 22, and the sample positioned inthe cell when the cell is placed in oven 24.

In order to communicate an extraction fluid to the sample for extractionof analytes therefrom, automated extraction apparatus 21 furtherincludes a fluid communication assembly, which is comprised of aplurality of components. Briefly, the fluid communication assembly ofthe present invention preferably includes an extraction fluid reservoir26 in which an extraction fluid 27, such as a solvent, is positioned. Apump 28 is coupled in fluid communication with reservoir 26, forexample, through conduit 29. It will be understood, however, that pump28 can be replaced by a high pressure source or other actuator whichwill cause flow of solvent 27 from reservoir 26 through conduit 29 tocell 22, as will be described in more detail below. The fluidcommunication assembly further preferably includes a pump valve 31between conduit 32 and subconduits 33 and 34, which are connected topump 28. It is possible to eliminate valve 31 and merely meter solventflow by pump 28, which is preferably provided by a positive displacementpump in which each stroke produces a metered amount of fluid. Conduit 32may have a pressure transducer 36 mounted therein which is operablyelectrically coupled to a controller, generally designated 37 (throughelectrical conductors, not shown) for the transmission of transducersignals to the controller. A check valve 38 and purge valve 39 can beprovided in branch conduit 41 from the pump conduit 32 for use in amanner which will be described in more detail below. Similarly, a reliefvalve 42 can be provided in branch conduit 43 for relief of pressure inconduit 32 to waste receptacle 52 or atmospheric vent 55.

An end portion 44 of pump conduit 32 provides and acts as an inletconduit to cell 22 for the flow of extraction fluid into the samplecontainment cell. Similarly, a conduit 46 also coupled to cell 22 actsas an outlet conduit from the cell and is part of the fluidcommunication assembly. Mounted in outlet conduit 46 is a static valve47, the operation of which will be described in more detail below, andthe end or needle portion 48 of outlet conduit 46 is received in acollection vial 252. In the preferred form, collection vial 252 is alsovented by vent needle 272 and vent conduit 51 to waste receptacle 52 ordirectly to atmospheric vent 55.

Also included in the extraction fluid communication assembly can be thefollowing additional elements, purge gas reservoir 53, with associatedconduit 54, regulator 56 in branch conduit 57, which communicatesthrough regulator 59 and on-off valve 58 with the reservoir 26 tooptionally pressurize the solvent reservoir 26. Also optionally providedcan be a relief valve 61 mounted in conduit 54 which terminates in atoggle valve 62, enabling toggling between a source of house air 63 andpressure reservoir 53, at the user's option in order to drive apneumatic manifold, generally designated 64. Manifold 64, generally, isemployed to control the various valves in the fluid communicationassembly and to control the operation of various actuators comprising amanipulation assembly of the automated extraction apparatus 21 of thepresent invention.

Moving now to the components comprising the manipulation assembly, thereare three actuators which are primarily concerned with cell manipulationin apparatus 21. First, pneumatic actuator or piston cylinder assembly66 is coupled to move cell 22 between cell tray 23 and oven 24. Actuator66 can be a double-acting piston and cylinder assembly controlled byvalves 66a and 66b. Actuator 67 carries a portion of the fluidcommunication assembly, namely, inlet conduit 44 and outlet conduit 46,and moves the same into engagement with, and preferably sealedengagement with, cell 22. Pneumatic actuator or piston and cylinderassembly 68 is coupled to a cell clamping device schematically shown at221 in order to clamp cell 22 while in oven assembly 24 for sealingpurposes, which will be described hereinafter.

Broadly included in the expression manipulation assembly in extractionapparatus 21 of the present invention is a further actuator 71, which iscoupled to displace outlet conduit needle 48 and vent conduit needle 272carried in a common assembly 72 sometimes referred to as the "needle"assembly.

Finally, cell tray 23 preferably is movable and mechanically coupled at73 to a motor 74, while vial tray 76 similarly is movable and coupled at77 to a motor 78. Motors 74 and 78 are electrically connected tocontroller 37, by conductors which are not shown.

Referring now to FIG. 10, a sample containment cell 22 which isparticularly well suited for use in extraction apparatus 21 is shown.Sample containment cell 22 has a body 101 which is preferably hollow anddefines a sample-receiving cavity 102 therein. At least one opening, andin the form illustrated two end openings 103 and 104, are provided incell body 101 in order to enable positioning of a sample from which ananalyte is to be extracted in cavity 102. Removably mounted on the endof body 101 is at least one closure member or end cap 106, which ispreferably threadably secured on threads 107 by a threaded insert member108 carried by and secured to cap 106 by a retainer spring clip or ring118. The opposite end cap 109 is constructed in a similar manner andthreaded at threads 111 in the same fashion as cap 106, and accordinglywill not be described in more detail herein.

Extending from an exterior of cell 22 to cavity 102 is a fluidpassageway structure. In the preferred form, the cell fluid passagewaystructure provided by an inlet passageway or bore 112 and an outletpassageway or bore 113, each of which extend through end caps 106 and109, respectively. Passageways 112 and 113 allow an extraction fluid tobe injected or pumped into cavity 102 through inlet passageway 112 andout of the cavity through outlet passageway 113.

As the apparatus and process of the present invention are particularlywell suited for solvent extraction at elevated temperatures andpressures, it will be appreciated that an important aspect of thepresent apparatus will be that the high temperature and high pressuresolvent in cavity 102 must be contained. Leakage of such fluids canpresent a substantial safety hazard and can result in contamination ofsubsequent samples when multiple cells are sequentially processed usingthe apparatus of the present invention.

Accordingly, cell 22 preferably further includes a closure sealassembly, such as a deformable annular sealing washer 114, and apassageway sealing assembly 116, for example, in the form of adeformable O-ring. As will be seen, each end of cell 22 carries both theclosure sealing assembly 114 and the passageway sealing O-ring 116.

Cell 22 also preferably includes an end frit or filter disk 117 whichreduce channeling of the extraction fluid and prevent plugging of theoutlet passageway 113.

It is most preferable that body 101 and end caps 106 and 109 be formedof a corrosive resistant material, such as stainless steel, whichmaterial also is effective in containing pressures at elevatedtemperatures. It will be understood, however, that other cell materialsmay be preferable, depending upon the operating temperatures andpressures, as well as the solvent employed in the apparatus and processof the present invention.

Fluid Coupling To Cell

In a first important aspect of the apparatus and method of the presentinvention, the sample containment cell 22 must be fluid coupled to thefluid communication assembly for delivery of an extraction fluid 27 tocavity 102 in the cell.

Referring now to FIGS. 2, 4, 6A and 10, fluid coupling of cell 22 to thefluid communication assembly can be described.

As will be seen in FIG. 2, apparatus 21 preferably is implemented byrotatably mounting two turntables or carousels 23 and 76 to theframework 131 of the apparatus. An upper carousel or turntable providescell tray 23, which is best shown in FIG. 4. The cell tray assembly 23can include a support member 132 which is coupled by fasteners or thelike to a portion of framework 131. A rotatable turntable plate 133 ismounted on a spindle (not shown) which is coupled at opening 134 to amotor schematically represented in dotted lines as cell tray motor 74.The cell tray motor 74 is enclosed in an appearance housing above thecell tray.

As will be seen, the cell tray preferably includes a plurality ofcell-receiving support bays 136 having upwardly facing shoulders 137dimensioned to pass under and support a downwardly facing shoulder 138(FIG. 10) on cell 22. Accordingly, motor 74, which can be a steppingmotor or the like, is coupled by a shaft to rotate cell tray 23 so as tosequentially position cells 22 at an indexed location for fluid couplingto the fluid communication assembly of the present invention.

One of the highly desirable features about the construction of cell trayassembly 23 is that each of the loading bays 136 is constructed so as tosupport cells 22 of differing length. Since in each case cell 22 issupported by surface 138 on end cap 106 (or a corresponding surface oncap 109 if the cell is inverted), cell tray bays 136 will accommodate,for example, 11, 22 and 33 milliliter size cells. The cell length shouldnot reach down to support member 132. The upper end of the cell will, ineach case, be in the same height position for fluid coupling to thefluid communication assembly.

Referring now to FIG. 6A, the apparatus of the present invention whichproduces fluid coupling of the fluid communication assembly to cell 22can be described. Fluid coupling assembly, generally designated 141,includes actuator 67, which may advantageously take the form of adouble-acting piston and cylinder assembly coupled by pneumatic conduits142 through a switching valve 143 (FIG. 1) to pneumatic controlmanifolds 64. In the assembly, piston rod 144 is stationary and fixed at146 to the upper assembly arm member 147. As air is switched by valve143 from one side to the other of piston 144, the cylinder housing 148is reciprocated on guide rods 149 and 151 in an upward or downwarddirection. The guide rods are secured at upper ends 152 to the upper armmember 147 of the assembly frame and at the lower ends to a lower framemember 153.

Carried on reciprocating housing 148 is a lower arm 154 which extendsoutwardly and laterally to an end 156 that carries a rigid conduit 157coupled to flexible conduit 158. Conduit 158 must accommodate movementof the lower arm by its own flexibility or a flexible joint, not shown.

The stationary upper arm 147 has an end 159 that carries a rigid conduit161 that is fluid coupled to conduit 162. In the preferred form of thepresent invention, conduit 162 and rigid conduit 161 together comprisethe fluid communication assembly inlet conduit, generally designated 44,which is in the fluid system as shown in FIG. 1. Similarly, the flexibleconduit 158 and rigid conduit 159 together comprise the outlet conduit46 of the fluid communication assembly.

As will be seen in FIG. 10, the end of the rigid conduits 161 and 157each have mounted thereon a nozzle member 163 which is formed with afrusto-conical tapered surface 164 and an injector nose 166 having acentral opening therein substantially corresponding in diameter to thediameter of cell passageway bores 112 and 113. As also will be seen fromFIG. 10, the frusto-conical surface 164 mates with a similar conicalrecess in the caps so as to automatically cause cell 22 to come intoalignment with nozzles 163 as the nozzles are driven into the cell capsby actuator 67. Moreover, the mating tapered or conical surfaces in thenozzle and cap provide gripping stability for movement of the cell, asis set forth below.

Operation of the actuator to effect fluid coupling can now be described.Since upper cap 106 is always at the same height as it is brought to thefluid coupling assembly 141 by rotatable carousel 23, the upper arm 159may be fixed and rigid conduit 161 extend down by an amount which barelyclears the top surface of cap 106. The cap, as supported by shoulder 138on shoulder 137, with the cell depending therefrom, can therefore berotated by tray 23 freely under conduit 161, which clears the outermostportion of the carousel as it rotates. When tray motor 74 rotates aselected bay 136 into substantial alignment with the stationary inletconduit 161, the motor is stopped. While carousel 23 is rotated, arm 154with movable outlet conduit assembly 46 is in a lowered position, whichis sufficiently below end cap 109 for the longest of the cells which canbe placed in carousel 23, that it will clear the lower end cap. Once thecarousel is indexed, valve 143 can be switched to drive arm 154 upwarduntil the rigid conduit 157 of the outlet conduit assembly 46 engagescap 109. As tapered surface 164 engages a mating tapered surface in cap109, the cell tends to come into precise axial alignment with the lowernozzle 163. The fluid actuator 67 continues to drive movable housing 148and arm 154 upward, carrying outlet conduit assembly 46 upward andseating lower nozzle 163 in the frusto-conical recess in cap 109. Lowernozzle 163 and conduit 157 begin to lift the cell slightly off shoulder137 so as to drive the cell upwardly into the upper nozzle 163 of theinlet conduit assembly 44. The tapered surface on the upper nozzle 163similarly aligns and seats against the mating tapered surface in cap106.

In the preferred form, actuator 67 continues to drive the lower oroutlet conduit assembly 46 upwardly until the protruding noses 166 aredriven into deformable passageway seals 116 carried by the upper andlower cell caps. The passageway seals are deformed into sealingengagement with noses 166 in both inlet conduit 44 and outlet conduit46. Thus, cell manipulating actuator 67 is formed to move at least oneof the inlet conduit 44 and the outlet conduit 46 into engagement withcell 22 to fluid couple the inlet conduit and outlet conduit to thepassageway structure of the cell, namely, bores 112 and 113. In thepreferred form, this engagement is a sealing engagement in which thecell manipulating assembly effects sealing between the nozzle on inletconduit rigid tube 161 with end cap 106 and the sealing assembly 116carried thereby. Similarly, in the preferred form, the outlet conduitnozzle is driven into sealing engagement with the seal 116 carried byend cap 109.

One of the advantages of the apparatus of the present invention is thatthe sealing assemblies 116 are carried by the cap, rather than by thefluid communication apparatus. If a sealing assembly should fail, onlythe particular cell involved will be at risk and the likelihood ofcontamination will be lessened. The next cell in carousel 23, forexample, may have perfectly good passageway structure seals 116 and thefailure of preceding passageway seal assembly will not require shutdownof the present apparatus.

As will be appreciated, one method of controlling actuator 67 is bymonitoring the fluid pressure with a pressure transducer so as to sensewhen lower movable arm 154 has produced sealing engagement of theassembly with cell 22. In the present invention the fluid pressuresupplied to actuator 67 is merely left on so as to apply a maximumdesigned force to conduits 44 and 46, and the vertical position ofhousing 148 during reciprocation can also be sensed using opticalsensing means. For example, an optical sensor support panel 171 can bemounted between stationary upper arm member 147 and stationary lower armmember 153 by mounting screws or fasteners 172. Carried by panel 171 area plurality of optical sensors 173a, 173b and 173c (best seen in FIG.6B) which sensors are electrically connected by conductors (not shown)to controller 37. Mounted to the back surface of movable actuatorhousing 148 is a Z-shaped flange 174 (FIG. 6B) which has an outer leg(not shown) which passes between the two sides of the optical sensors173a, 173b, and 173c. As actuator housing 148 reciprocates vertically,therefore, the flange of member 174 passes through optical sensors 173a,173b, and 173c to indicate the position of housing 148 and therebyenable controller 37 to sequence the fluid flow to sealing of theconduits to cell 22, depending upon the cell height. Panel 171 can havethe sensing cells fixed thereto or they can be movably mounted to thepanel, and controller 37 can be responsive to signals received fromsensing cells 173a, 173b, and 173c to sense the position of the movableconduit arm 154.

As will be described in more detail below, the cell manipulatingassembly 141 of FIG. 6A also preferably is mounted for rotation by ashaft 181 in bushings or bearings provided in fixed upper arm 147 andfixed lower arm member 153. This shaft 181 is best seen in FIG. 6B. Thesensor panel 171, therefore, can also include a sensor 182 which isturned by 90 degrees relative to sensors 173a and is also an opticalsensor electrically connected to controller 37 by conductors which arenot shown. Sensor 182 can be used to sense the presence or absence of aflange member which is stationary or unmovable relative to framework 131so as to provide feedback to the control as to the angular position ofthe entire assembly 141.

Transport Of Cell Assembly

In the preferred form of the apparatus of the present invention, cellassembly 22 is not only filled with fluid by the fluid communicationassembly and thereafter pressurized, in a manner which will be describedbelow, but it is also heated by an oven assembly 24. In a simplifiedform of the apparatus of the present invention, sample containment cell22 can be manually placed directly in an oven assembly or other cellsupport structure. The fluid communication assembly can then be broughtinto fluid coupling with the cell assembly, as above described. Thiswould be the case, for example, if FIG. 6A were surrounded by an oven.In the preferred form, however, an oven assembly is positioned proximatethe cell supporting structure or tray 23 and the cell assembly istransported from the tray to the oven for elevation of the extractionfluid inside the cell assembly to enhance extraction effectiveness.Accordingly, in the preferred form of the invention, the apparatus cellmanipulating assembly is formed for the movement or transport of cellsfrom tray 23 to oven 24.

It is an important feature of the apparatus of the present invention,however, that transport or movement is accomplished by gripping cell 22between inlet conduit 44 and outlet conduit 46 and then moving the cell,as gripped by the inlet and outlet conduits, between the tray and oven.Thus, in the preferred form, the cell manipulation assembly is formed tomove at least one of the inlet and outlet conduits into engagement withthe cell to fluid couple the cell to the fluid communication assemblyand to substantially simultaneously grip the cell between the conduitends. The cell manipulation assembly further is formed to move the cellas gripped between the inlet and outlet conduit between the tray andoven assembly.

In FIG. 6A assembly 141 has fluid coupled the fluid communicationassembly to cell 22 while the cell is positioned substantially at aloading station or area at the carousel or tray 23. This is the positionof arm assembly 141 in FIG. 2. In FIG. 6B the arms 147 and 153 have beenrotated in a counterclockwise direction from FIG. 6A to a position atwhich cell 22 will be surrounded by the oven. This moved or ovenposition is also shown in FIGS. 3 and 4.

Accordingly, in the present invention the cell manipulation assembly isused to produce a fluid coupling and is further used to grip the cell ina stable condition between the frusto-conical conduit noses 163 andtransport it between a support, such as carousel tray 23, to a proximateheating device, such as oven assembly 24. When the cell is inserted inthe oven by pivoting of assembly 141 about shaft 181, the cell willstill be fluid coupled to the fluid communication assembly portion ofapparatus 21. Thus, as fluid coupled, extraction fluid can becommunicated to cavity 21 of the cell and the cell simultaneouslyheated. Moreover, the pressure inside cavity 102 can be elevated so thatthe combination of elevated temperature and pressure increases theeffectiveness of analyte extraction.

As best may be seen in FIGS. 3 and 6B, shaft 181 is coupled by mountingblock 191 to the housing framework 131 so that articulation between thepositions of FIGS. 2 and 3 can be accomplished by displacement ofassembly 141. The rotatable displacement of assembly 141 about shaft 181is driven by actuator 66 (FIG. 1) which can be coupled to any portion ofassembly 141 which is not vertically displaced, such as the upper arm147, and be supported by a stationary portion of frame 131. Again, thesensor 182 senses the angular position of assembly 141. In the mostpreferred form, actuator 66 will drive or rotate assembly 141 from theloading station at the cell to the oven station or heating stationinside the oven and further overdrive slightly so that the side walls ofbody 101 of the cell are in contact with portions of oven 24 forconduction heating of the cell.

This is not an absolute requirement in that the oven assembly canoperate as a radiation and/or convection heater, but heat transfer isimproved by overdriving the rotation of assembly 141 into oven 24 untilthe body and/or end caps of the cell are engaged with the oven.

Oven Assembly

In the apparatus of the present invention, the preferred form of ovenassembly 24 is shown in FIG. 5. The oven has a generally U-shaped metalbody 201 which is elongated and open to one side 202 for pivotal receiptof cell 22 into the oven. Mounted in bores extending longitudinally inoven 24 is at least one resistance heater or thermal cartridge 203. Inthe preferred embodiment two cartridges 203 extend over substantiallythe entire length of oven body 201 and are coupled by electricalconductors 204 to a source of electricity which is controlled bycontroller 37. Mounted in between thermal resistance heating cartridges203 is a temperature sensor 206 which is electrically connected toprovide sensing signals through conductors 207 to controller 37. As willbe seen, the interior of U-shaped body 201 preferably is formed withnotches 208 dimensioned to slidably receive the top and bottom caps 106and 109 of cells of varying lengths. The notches 208 are dimensioned forsliding receipt of the cell caps therein, but the upwardly facingsurfaces 209 of the lower three notches 208 are intended to engage thedownwardly facing surface of the lower cap 109, in a manner which willbe described in more detail hereinafter.

It is preferred that oven assembly 24 include an outer insulated housing211 which substantially encloses the oven body and includes an open side212 to which a displaceable door structure, such as brush bristles 213,are mounted. A similar bristle assembly preferably covers the, topopening 214, but is not shown for simplicity of illustration.Accordingly, as transport or cell manipulation assembly 141 rotates cell22 into the oven, the cell displaces brush bristles 213 which thenspring back to close or reduce the heat transfer out the open side andopen top of the oven. As will be seen from FIG. 3, the upper arm 159 ofassembly 141 essentially covers the upper opening on the top of oven 24,while the lower arm 154 reaches into the oven from the side, such thatthe bottom of the oven may be substantially closed and does not requirea brush or other door closure. As will be appreciated, other forms ofdoors or closure on oven 24 are suitable for use with the presentinvention.

A further important feature of the present invention is that ovenassembly 24 includes a cell clamping device or assembly 221. As can beseen from FIG. 5, oven assembly 24 is mounted on two verticallyextending side-by-side post assemblies 220. Each of post assemblies 220may advantageously formed as an elongated tubular sleeve member 222 inwhich a pair of rod members 223 are slidably telescoped. The bottom ends224 of sleeves 222 rest on a member 226 which is attached to an actuatorpiston 225 of compression or clamping actuator 68. The upper end 227 ofsleeves 222 bears upon an outward laterally extending ear 228 which isfixedly secured to oven body 201. Posts 223 extend slidably out througha bearing end ear 228 and up through an upper pair of ears 229 to anuppermost clamping member 231. The upper ends of rods or posts 223 aresecured by nuts or the like 232 to the clamping member 231.

In operation, when actuator 68 is pressurized by controller 37 andpneumatic manifold 64, piston 225 is driven upwardly and carries sleevesupwardly on posts 223. The lower ends of posts 223, not seen, aresecured to stationary plate 233 that is fastened at 234 to thestationary portion of actuator 68. Accordingly, the piston displacementcauses the sleeves to rise while the posts 223 are held in position. Assleeves 222 rise on posts 223, they carry ears 228 which are attached tothe oven body upwardly towards the upper clamping member 231. Theintermediate ears 229 provide guidance to avoid misalignment.

As schematically may be seen in FIG. 10, the upwardly facing ledge orsurfaces 209 in the lowermost notch 208 of the oven assembly engages theoppositely facing surface 235 on lower cap 109. Conversely, thedownwardly facing surface 236 of upper clamping member 231 engages theupwardly facing surface 237 of the upper cap 106.

As the oven body 201 is driven upward by clamping sleeves 222,therefore, an axial clamping force is applied on each end cap 106 and109 in an inward direction toward cavity 102. This oven inwardlydirected clamping force, in turn, tends to drive each end cap or closuremember against the seal assemblies 114 between the cap and cell body101. As will be seen from FIG. 10, the end surfaces of body 101 make aface contact with sealing gaskets 114 and the oven clamping assemblyaugments or enhances this seal between the removable end caps and thecell body.

Additionally, it is a very important feature of the present inventionthat up as many as three separate clamping forces may be applied whichtend to clamp the end caps 106 and 109 against the annular seals 114 andthe seals against the annular ends of the cell body 101. First, as justdescribed, the clamping forces in oven 24 apply an inward force to eachend cap which drives the end cap toward the seal and toward the cellbody.

Second, and independent of the clamping force in the oven clampingassembly 221, actuator 67, which drives inlet conduit 44 and outletconduit 46 into sealed engagement with the end caps, also applies anaxial inward force on the end caps toward seals 114. This inward sealingforce would be present even if there were no oven clamping device.Third, the threadable mounting of end caps 106 and 109 on body 101allows an inward axial force to be applied to the seals by simplyfinger-tight screwing the end caps down on the cell body. As will beseen in FIG. 10, the threads will permit tightening beyond the thicknessof seal assemblies 114. This finger-tight sealing of the end capssimilarly does not require an oven clamping device, or for that matterthe conduit gripping of the cell.

The three inward force-producing structures have the following relativeeffect on sealing cavity 102. By applying the conduit pressure requiredto seal the inlet and outlet conduits to the passageways through thecap, the cell 22 can withstand a pressure in cavity 102 of about 100-200psi. Finger-tight screwing of end caps 106 and 109 down on body 101 willallow the internal pressure in cavity 102 to be raised to about 1500 to2000 psi. The cell clamping device allows the pressure in cavity 102 tobe raised to as high as 3000 to 4000 psi.

One of the important features and aspects of using a fluid actuator 67to drive conduits 44 and 46 into sealed relation with the end caps isthat if runaway pressure should build up in cavity 102, the maximumpressure which can be applied by actuator 67 can be limited to apressure below a pressure which cell body 101 can withstand.Accordingly, if the pressure inside cavity 102 exceeds the maximumpressure at which conduits 44 and 46 can be driven against passageway116, what occurs is that the excess pressure in cavity 102 will blow outor blow by conduits 44 and 46 by backing them out of the cap recesses.While this creates a certain messiness, it is highly desirable ascompared to rupturing cell body 101, and it provides another failsafefeature for the present apparatus.

Returning to FIG. 5, it is preferable that actuator 68 not be adouble-acting cylinder and that a biasing spring be provided to returnthe sleeves and piston to the lowered position. Thus, a compression coilspring 241 can be mounted around each of posts 223 between the upperears 229 and the clamping member 231. When the actuator pressure isdropped by valve 242 (FIG. 1) springs 241 will return the clampingdevice to an open position and permit removal of cell 22 from oven 24.As can be seen from FIG. 1, valve 242 is mounted in a branch conduit243, which branches off of conduit 57 from compressed gas reservoir 53.It would be possible to run oven clamping actuator 68 from manifold 64,but in the preferred form gas reservoir 53 is used to run actuator 68because the force required to reach the maximum clamping pressureusually cannot be achieved through most house air supplies.

It is further preferable that the automated analyte extraction apparatusof the present invention include a collection vial rack assembly,generally designated 76 which best may be seen in FIGS. 2, 7 and 8. Thecollection vial assembly 76 is formed to support and manipulate aplurality of collection vials 252, which are to be positioned forreceipt of extraction fluid 27 after it has been passed through cell 22and out of outlet conduit 46. In the preferred form, collection vialassembly 76 includes a vial supporting rack or carousel 253 which can berotatably mounted to a base structure 254 secured to the framework 131of apparatus 21. Drive motor 78, schematically shown in dotted lines inFIG. 8, is mechanically coupled to drive turntable or carousel 253 andis electrically coupled to controller 37. Controller 37 can step motor78 so as to bring each of collection vials 252 into an indexed relationrelative to needle assembly 72, which positions the discharge needle 48of outlet conduit 46 inside vial 252 and simultaneously positions ventconduit needle 272 of vent conduit 51 for communication with the insideof vial 252. Each of the rack bays 256 of carousel 253 is formed forreceipt and support of vials 252 in a stable generally upright position.The bottom surfaces 257 of bays 256 provide the downward support forvials 252. The vials 252 are not supported by their caps 258, butinstead by the bottom surfaces as they seat on bay surfaces 257. Inorder to accommodate collection vials of varying height and volume,insert plugs 259 can be mounted in bays 256 so that the upper surface261 will support the bottom of a shorter vial with cap 258 at the samevertical elevation for delivery of extraction fluid thereto by needleassembly 72.

In the preferred form, collection vials 252 are constructed as isconventionally known in the industry. The caps 252 have a central openarea which is covered by a rubber diaphragm 262. The bodies 263 of thecollection vials are preferably transparent to an optical sensor, suchas an infrared sensor, although the vials are often formed of a darkamber glass to minimize degredation of the extraction fluid by visiblelight. As can be seen from FIG. 1, it is preferable that both thedischarge needle 48 and needle 272 of vent conduit 51 be inserted intocollection vial 252 through diaphragm 262. This can be mostadvantageously accomplished by inserting both elements simultaneously byusing needle assembly 72.

FIGS. 9A through 9C illustrate the sequence of movement of needleassembly 72, as it is moved from a retracted position shown in FIG. 9Ato a fully installed position shown in FIG. 9C.

In the preferred form, the end of outlet conduit 46 is coupled to amovable arm 271 which is mounted for both rotation about a vertical axisand vertical displacement. Similarly, vent conduit 51 is carried by arm271, and each of these conduits are coupled to hollow fluid transmittingneedles 48 and 272. Arm 271 extends laterally outwardly of, and is fixedfor movement with, vertically displaceable member actuator 71, which isreciprocably mounted on piston shaft 274. The actuator piston isanchored to C-shaped bracket 276. Needle assembly actuator 71 is adouble-acting actuator having control valve 277 (FIG. 1).

As best may be seen in FIG. 7, a roller-type follower 280 is mounted ona back side 285 of actuator 71. Positioned proximate follower 280 is adownwardly facing, sloping cam surface 290 (FIGS. 9A-9C) whichterminates in a vertically extending cam surface 295. When actuator 71is raised on piston 274, cam follower 280 is driven up into cam surface285. The upward incline of surface 285 produces pivoting of bracket 276and arm 265 on which it is mounted in a clockwise direction about axle278 against tension spring 260. This brings the assembly to the FIG. 9Cposition.

To insert needles 48 and 272 into vial 252, the controller switchesvalve 277 and spring 260 rotate arm 265 and bracket 276 in acounterclockwise direction. Follower 280 follows downwardly sloped camsurface 290 and, that together with pressure on the other side of thepiston, causes actuator 71 to fall and needles 48 and 272 to bepositioned just over the diaphragm 262.

As the assembly reaches the position of FIG. 9C, follower 280 reachesvertical cam surface 295 and continued pressure on the bottom side ofthe piston drives the needles down through diaphragm 262 to the finalposition of FIG. 9C.

To withdraw the needles, the pressure is applied to the top side of thepiston and actuator 71 is raised until roller follower 280 engage thecam surface 290, at which point the needles have cleared diaphragm 262and the slope causes rotation in an opposite direction.

Also mounted on framework 276 is a vial-receiving channel 279 formed tomate with a side of the vial body. Channel 279 carries a plurality ofoptical emitters 281a-281f, which communicate a sensing beam throughorifices in shell 279 and through the body 263 of collection vial 252 tothe opposite side of the shell where the beam is received. The opticalsensors 281a-281f are electrically connected to controller 37 byelectrical conductors (not shown) as are the corresponding detectors onthe opposite side of shell 279.

In operation, the needle subassembly is out of aligned position withvial 252 until the vial is brought to an indexed relation to the needleassembly. When controller 37 senses that motor 78 has driven theselected vial 252 to the indexed position, needle assembly 72 rotates ina counterclockwise direction as shown in FIGS. 9A-9C toward vial 252.

As the framework is rotated about axle 278 in the counterclockwisedirection to the position of FIG. 9C, actuator 71 drives needles 48 and272 through rubber diaphragm 262 and into collection vial 252 forcommunication of extraction fluid from cell 22 to vial 252.

Extraction Process

Having described the preferred embodiment of the extraction apparatus ofthe present invention, operation of the apparatus and implementation ofthe process of the present invention can be described in detail. Thedescription will be in terms of the preferred embodiment, which includesa plurality of extraction cells, which are sequentially moved throughthe extraction apparatus with fluid being sequentially collected in aplurality of collection vials. It will be understood, however, that thepresent apparatus can be used with a single sample containment cell anda single collection receptacle.

The first step is to fill one or more cells 22 with the desired samples,usually in the form of a solid matrix sample, from which an analyte isto be extracted. The filling step is accomplished manually by unscrewingone of the end caps 106 and 109 on cell 22 and placing the desiredamount of sample in cavity 102. Next, one or more cells 22 is installedin the cell tray or carousel 23 in the respective bays, where the cellsare supported by their upper end caps 106. Similarly, a correspondingnumber of vials 252 are mounted in the collection rack or carousel 253by a manual operation.

Next an extraction solvent, or in the case of supercritical fluidextraction, an extraction fluid 27, is placed in solvent reservoir 26and a solvent reservoir coupled to conduits 57 and 29 of the fluidcommunication assembly. Using user input keyboard 291 in controller 37,the process of the present invention can be started. Motor 74 isactuated by controller 37 to rotate cell carousel 23 so as to index aselected one of cells 22 at a fluid coupling station for gripping andfluid coupling of the cell by the cell manipulating assembly 141. At thesame time, controller indexes a corresponding collection vial 252 at anindexed position for coupling of outlet conduit 46 to the collectionvial through needle assembly 72. The motion of the vial rack 76 orcarousel 253 is controlled by motor 78 and controller 37. Once the celland collection vial are appropriately positioned between the rigid inletconduit end 161 and the rigid outlet conduit end 157, the controlleroperates actuator 67 so as to cause the outlet conduit 157 to be drivenup into the bottom cell cap 109 so as to fluid couple the cell to thefluid communication system of the apparatus and simultaneously grip theapparatus between inlet conduit 44 and outlet conduit 46. Once fullgripping has been sensed through sensors 173a, 173b, or 173c, actuator67 holds the cell between the inlet and outlet conduits. The cell is nowslightly elevated with respect to turntable 23 and, therefore, free tobe moved.

It should be noted that rigid conduit portions 157 and 161, in fact,surround the conduits 46 and 44 which pass concentrically therethroughto nozzles 163. These conduit portions are designed to provide thegripping strength necessary for gripping cell 22', which strength wouldnot normally be present in the small diameter conduits 44 and 46, whichare all that are required for the relatively low volumetric flow of theextraction solvent.

Next, controller 37 operates actuator 66 which rotates assembly 141about shaft 181. Two independent valves 66a and 66b are provided so thatthe actuator can be stopped or parked in either the position next to thecarousel 23 (at the end of each cycle) or the oven position. Actuator 66drives assembly 141 from the position shown in FIGS. 2 and 6A to theposition shown in FIGS. 4 and 6B, at which point the cell 22 is urgedinto contact with the oven for better heat transfer.

The angular position of assembly 141 can then be sensed by sensor 182 sothat the controller 37 can tell when cell 22 is fully advanced into ovenassembly 24.

With cell 22 in oven assembly 24, controller 37 now actuates ovenclamping device 221. This is accomplished by operating actuator 68against a spring biasing force by springs 241. The combination of cellthreads, actuator 67 producing gripping between the end caps andclamping device 221 effectively seals end caps to cell body 101 as wellas sealing inlet conduit 44 and outlet conduit 46 to the cell passagewaystructure. During the process of fluid coupling the cell to the fluidcommunication assembly and moving the cell by the fluid inlet and outletconduits to the oven, the controller can also move needle assembly 72from the retracted position to a position at which the needles 48 and272 are driven down through the rubber diaphragm 262 and into collectionvial 252.

Apparatus 21 is now ready for commencement of the extraction cycle orcycles.

Once both the cell and receiving vial are coupled for fluidcommunication of extraction fluid or solvent 27 through the system,controller 37 opens pump valve 31 and static valve 47 through thecorresponding manifold valves 31a and 47a. As illustrated, pump 28 is adouble headed pump for smoother fluid output but a single headed pumpalso may be used. Pump 28 is started and solvent 27 is drawn fromreservoir 26, with the aid of a slight pressure head from gas source 53through conduits 54 and 57. The solvent or extraction fluid is pumpedthrough conduit 29 and one of conduits 33 or 34 to conduit 32, whichterminates in the inlet conduit 44 inside rigid conduit portion 161,with nozzle 163 that injects solvent through inlet passageway 112 incell 22.

The pump continues to operate until cavity 102 is filled with solventand solvent begins to exit outlet passageway 113 and out the outletconduit assembly 46 carried inside rigid conduit member 157. The exitingextraction fluid passes along conduit 46 to needle assembly 72 andbegins to be forced out of needle 48 and into collection vial 252. Whenthe extraction fluid in collection vial 252 reaches the first orlowermost optical sensor 281a, a signal is sent to controller 37 whichcloses the static or outlet valve 47.

It should be noted that during the pumping process the pressure incavity 102 of the fluid will rise as a result of the resistance to flowthrough the cell produced by the small bores 112 and particularly bore113. Additionally, the solid matrix material of the sample resists flow,as do the two frits mounted across the inlet and outlet passageways.Accordingly, pressure has already begun to rise in cell 102 when staticor outlet valve 47 is closed. The closure of outlet valve 47, however,produces a further rise in the cell, which is transmitted upstream topressure transducer 36. The pressure transducer then sends signals tocontroller 37 as to the pressure in conduit 32 and thus cavity 102 ofcell 22. When the pressure reaches a predetermined level, which can beinput through keyboard 291 to controller 37, the controller maintains apressure controlled valve using, as needed, incremental strokes of thepump.

In the preferred form of an assembly 24 will be operating at apredetermined elevated temperature, as controlled by signals fromthermocouple 206 in the oven assembly. Accordingly, when cell 22 ismoved from the cell tray 23 to heater assembly 24 it will enter thepre-heated oven and temperature will begin rising in the extractionfluid as soon as it reaches the cell. As will be appreciated, the risingtemperature of the extraction fluid in cell cavity 102 can produce itsown pressure rise in the cavity. Accordingly, as the extraction fluidtemperature rises there is the possibility, and likelihood, that thepressure will exceed the target pressure for the cell, and if transducer36 senses a pressure rise above the targeted or predetermined pressure,controller 37 will open static valve 47 for a short time so as to reducethe excess pressure in cavity 102. This pulsing of outlet valve 47results in small quantities of extraction fluid passing through needle48 to vial 252, but the quantities are very small as compared to theoverall sample.

Through the use of gate valve 47, a substantial equilibrium temperatureand pressure will be reached inside cavity 102 and the controller willallow this equilibrium condition to remain during a "soak" portion ofthe processing cycle of a predetermined length. The soak time can againbe input at keyboard 291 so as to correspond to the desired extractiontime for the particular matrix material in cavity 102. As will beunderstood, controller 37 will include a storable memory which can beprogrammed in a conventional manner so as to enable the soak time foreach sample cell to be the same or different, as determined by the user.

Once the predetermined soak time at the desired temperature has beencompleted, the fluid communication assembly purges or flushes theextraction fluid in cavity 102 into collection vial 252. This isaccomplished by opening outlet 47 to vial 252. The pump responds to thedrop in pressure for a predetermined number of strokes. The pump ispreferably a pneumatic, volume-displacement pump which causes a meteredamount of solvent to enter line 32 and thereby be forced into cellcavity 102. Thus, the cell cavity 102 is flushed with a new aliquot ofsolvent and the solvent which has soaked in cavity 102 is expressed outoutlet conduit 46 and needle 48 into collection vial 52.

At this point it is possible to withdraw needle assembly 72 fromcollection vial 252 by operation of the needle assembly actuator 71.Vial rack 76 can then be rotated by motor 78 and a new vial positionedfor receipt of the second aliquot of solvent or extraction fluid.

Alternatively, the original collection vial 252 can remain in place fora second or repeat soak for a fixed length of time, which can be thesame or different as the first soak. Again, the controller allowsequilibrium in the pressure and temperature to be reached using staticvalve 47 and then soaks the sample for the second soak time. It will beappreciated that virtually any number of Solvent extractions soak cyclescan be employed, although at some point the capacity of vial 252 will beexceeded and a second or third vial will have to be repositioned toreceive the flushed out solvent after soaking.

At any time after the first soak, as programmed by the controller,apparatus 21 can purge or flush the extraction fluid from cavity 102with an inert gas, rather than with additional solvent. The gas flush orpurge process is accomplished by closing inlet valve 31, or disablingthe pump opening outlet valve 47, and opening purge valve 39 so as topressurize conduit 32 with a gas from reservoir 53. The gasadvantageously can be nitrogen which will be driven in through inletconduit 44 and passageway 112 to cell cavity 102. The flushing gas willthen drive the extraction fluid from cavity 102 and from the matrix outthrough cell passageway 113 and outlet tubing or conduit 46 tocollection vial 252. An advantage of the gas flushing or purge is thatthe solid matrix sample is also dried by the purge so that when inletconduit 44 and outlet conduit 46 are uncoupled from fluid communicationwith cell 22, the cell does not drip extraction fluid from the outletpassageway 113. As above-noted, the gas purge can occur after the firstsoak or any subsequent soak, as determined by programing controller 37.

It should be noted that the second highest optical sensor 281b ispositioned on the sensor shell 279 so as to communicate a signal tocontroller 37 when the fluid level reaches a desired height forcollection vial 252, for example, one extraction cycle. An upper sensor281e communicates a fluid presence signal to the controller, thecontroller will prevent further filling of collection vial 252 andautomatically move to another collection vial. The uppermost sensor 281fon the sensor shell 279 is provided to sense the presence of acollection vial since it will be interrupted by the solid cap 258.Signals from sensor 281f, therefore, insures that the collection vial ispresent when the needle assembly is lowered so that extraction fluid isnot pumped out of needle 48 when no vial is present. Intermediatesensors 281c and 218a can be used with shorter vials or to providemultiple cycle sensing.

Once the purge of extraction fluid to vial 252 has been completed, valve39 is shut, allowing gas pressure in line 32 to return to openatmosphere pressure. Then valve 42, the relief valve, may be pulsed toassist in de-pressurizing line 32. Valve 68 allows oven clamping todisengage from cell, and then controller 37 operates actuator 66 throughvalve 66a to swing the cell gripping assembly 141 from the oven out tocell tray 23. Controller 37 thereafter operates valve 143 to drivedouble-acting actuator 67 in a direction uncoupling conduits 44 and 46from the cell by dropping arm 154 downwardly away from the cell. Cell 22then comes to rest on upwardly facing U-shaped shoulder 137 of the traybays 136.

In the preferred form of the process, the controller also includes arinse step in which the primary purpose is to remove any contaminationin outlet conduit 46 and needle 48 which would corrupt a subsequentextraction sample. The rinse cycle can be accomplished by rotating celltray 23 to a rinse cell mounted at a predetermined bay 136 in tray 23using motor 74. Similarly, vial rack 76 can be rotated to acorresponding rinse station position for a rinse vial 252. The actuator67 is then caused to fluid couple the inlet and outlet conduits with arinse cell 22 and actuator 71 causes needle assembly 72 to be insertedinto the rinse collection vial 252. For the rinse step, the rinse cell22 does not need to be moved into oven assembly 24, and accordinglyactuator 66 is not operated. The controller can instead simply openvalve 31 or enable the pump 28 and valve 47 and operate pump 28 to pumpa measured volume of solvent from reservoir 26 through the rinse cell,which has no sample in it and can have a reduced volume, so that theextraction fluid merely passes through the rinse cell to outlet conduit46. Once a measured amount has been pumped through the outlet conduit,it will rinse the extraction analytes from the previous sample fromoutlet conduit 46 and needle 48 into the rinse collection vial 252. Thiscleans the apparatus downstream of cell 22 so as to preventcontamination of the next extraction fluid which is collected using theapparatus of the present invention. After the rinse of solvent throughoutlet conduit 46, it is preferably to close valve 31 and open valve 39so that a nitrogen purge through the rinse cell and outlet conduit tothe rinse collection vial can be accomplished. This pushes the remainingsolvent into the collection vial and out of the outlet conduit 46.

In a typical loading of cell tray 23 and vial rack 76, there are fourrinse cell stations and four rinse collection vials, with the remainingcells and remaining vials being used for samples and the collection ofextraction fluid containing analytes.

At the end of the nitrogen purge of the rinse step, the purge valve 39is closed and the automated extraction apparatus can then begin anothersample extraction process by rotating the next sample cell 22 to thecell manipulation assembly 141.

What is claimed is:
 1. An apparatus for automated extraction of an analyte from a sample positioned in a cavity of a sample containment cell having a fluid passageway structure in communication with said cavity, said apparatus comprising:a loading tray constructed and arranged to support a cell having a cavity therein; an oven assembly mounted proximate said tray and operable for heating said cell and said sample positioned in said cavity when said cell is positioned in said oven; a fluid communication assembly mounted proximate said tray and including an inlet conduit and an outlet conduit constructed and arranged for selective fluid coupling to and uncoupling from a fluid passageway structure of said cell for communication of an extraction fluid to and from said cavity, said fluid communication assembly further being operable to produce an elevated pressure of said extraction fluid in said cavity; a cell manipulation assembly mounted proximate said tray, said inlet conduit and said outlet conduit being carried by said manipulation assembly, and said manipulation assembly being constructed and arranged to move at least one of said inlet conduit and said outlet conduit into engagement with said cell to fluidly couple said at least one of said inlet conduit and said outlet conduit to said passageway structure and to substantially simultaneously thereby grip said cell therebetween in a manner permitting fluid communication to and from said cavity, and said cell manipulation assembly further being constructed and arranged to move said cell, as said cell is fluidly coupled and gripped between said inlet conduit and outlet conduit between said tray and said oven assembly; and comprisinga controller coupled to said cell manipulation assembly and said fluid communication assembly for automatic control of fluid coupling and uncoupling with said cell, for control of the movement of said cell into and out of said oven assembly, for control of communication of extraction fluid to and from said sample in said cavity, and for control of the pressurization of said extraction fluid in said cavity.
 2. The apparatus as defined in claim 1 wherein,said cell manipulation assembly urges said inlet conduit and said outlet conduit into, and maintains said inlet conduit and said outlet conduit in, sealed engagement with said cell.
 3. The apparatus as defined in claim 2, anda cell structure having a passageway structure including an inlet passageway and an outlet passageway each communicating with said cavity, and said cell structure having a passageway seal assembly carried by said cell structure proximate each of said inlet passageway and said outlet passageway, said seal assembly being constructed and arranged to seal against said inlet conduit and said outlet conduit.
 4. The apparatus as defined in claim 2 wherein,said fluid communication assembly includes an extraction fluid reservoir, said inlet conduit being connected to said reservoir, a pump operably connected to said controller operable to pump said extraction fluid from said reservoir to said cell, and an inlet valve operably connected to said controller and positioned in said inlet conduit operable for selective opening and closing to pressurize said cavity and permit extraction fluid to be pumped from said cavity.
 5. The apparatus as defined in claim 4 wherein,said fluid communication assembly further includes an outlet valve positioned in said outlet conduit and operably connected to said controller to regulate pressure in said cavity and control the flow of extraction fluid through said cavity.
 6. The apparatus as defined in claim 5, anda fluid collection vial positioned to receive extraction fluid from said outlet conduit downstream of said outlet valve.
 7. The apparatus as defined in claim 4, anda fluid collection vial positioned to receive extraction fluid from said outlet conduit.
 8. The apparatus as defined in claim 1 wherein,said cell manipulation assembly is operable to grip said cell between said inlet conduit and said outlet conduit proximate opposite ends of said cell.
 9. The apparatus as defined in claim 8 wherein,said tray is constructed and arranged to orient said cell with a longitudinal axis of said cell in a near vertical orientation.
 10. The apparatus as defined in claim 1 wherein,said tray is constructed and arranged to receive and store a plurality of cells therein.
 11. The apparatus as defined in claim 10 wherein,said tray is mounted for movement; and said cell manipulation means is further operable to move said tray to position selected ones of said plurality of cells in indexed relation to said oven assembly for gripping between said inlet conduit and said outlet conduit.
 12. The apparatus as defined in claim 11 wherein,said tray is a carousel mounted for rotatable movement.
 13. The apparatus as defined in claim 11 wherein,said tray is constructed and arranged to receive and support cells of differing size in a position for movement between said tray and said oven assembly, and said tray is removably mounted to said apparatus.
 14. The apparatus as defined in claim 13 wherein,said cell manipulating assembly is operable for pivotal movement of said cells between said tray and said oven assembly upon gripping of said cells between said inlet conduit and said outlet conduit.
 15. The apparatus as defined in claim 1 wherein,said cell manipulating assembly displaces said inlet conduit and said outlet conduit toward and away from each other to grip said cell and to fluid couple said inlet conduit and outlet conduit to and uncouple said inlet conduit and said outlet conduit from said passageway structure of said cell.
 16. The apparatus as defined in claim 1 wherein,said oven assembly is constructed and arranged to receive said cell through a displaceable oven door structure.
 17. The apparatus as defined in claim 16 wherein,said door structure is provided by a brush assembly having displaceable bristles.
 18. The apparatus as defined in claim 1 wherein,said oven assembly includes a temperature sensor coupled to said controller.
 19. The apparatus as defined in claim 1 wherein,said oven assembly includes a movable clamping carriage and a support member, and said cell manipulation assembly is further operable to displace said movable clamping carriage relative to said support member between an open position, suitable for movement of said cell into said oven assembly, and a clamping position, applying a clamping force to said cell between said clamping carriage and said support member in a manner assisting a fluid-tight seal of said cavity.
 20. The apparatus as defined in claim 19 wherein said apparatus is intended for use with a cell having at least one removable end cap providing access to said cavity for insertion of said sample into said cavity, and wherein,said clamping carriage and said support member clamp said cell between said end cap and an oppositely facing surface on said cell.
 21. The apparatus as defined in claim 20 wherein,said clamping carriage is constructed and arranged to receive cells of varying size and urge said cells against said camping member.
 22. The apparatus as defined in claim 1 wherein,said oven assembly is operable for conductive heating of said cell; and said cell manipulation assembly applies a positive force to said cell urging said cell into contact with said oven assembly.
 23. The apparatus as defined in claim 1 wherein,said oven assembly is a U-shaped assembly formed with an open side dimensioned for movement of said cell into a position inside said U-shaped assembly, and said oven assembly includes at least one resistance heating element.
 24. The apparatus as defined in claim 23 wherein,said oven assembly is constructed and arranged to receive and heat cells of varying size.
 25. The apparatus as defined in claim 1, wherein,said fluid communication assembly further includes at least one fluid collection vial positioned for receipt of said extraction fluid from said cavity through said outlet conduit.
 26. The apparatus as defined in claim 25, anda collection manipulation assembly mounted proximate said tray and constructed and arranged for receipt and storage of a plurality of collection vials, said collection manipulation assembly further being operably connected to said controller and operable for movement of one of said fluid communication assembly and a selected one of said plurality of collection vials into a position for a receipt of said extraction fluid from said outlet conduit.
 27. The apparatus as defined in claim 26 wherein,said collection manipulation assembly includes a movable vial rack formed to receive and support said plurality of said collection vials therein.
 28. The apparatus as defined in claim 27 wherein,said vial rack is provided by a rotatable vial carousel.
 29. The apparatus as defined in claim 28 wherein,said collection manipulation assembly further carries a vent conduit of said fluid communication assembly, and said collection manipulation assembly moves said vent conduit between said retracted position and aid extended position for venting of said selected one of said collection vials.
 30. The apparatus as defined in claim 29 wherein,said vent conduit is fluidly coupled to a one of a waste reservoir and a vent.
 31. The apparatus as defined in claim 30 wherein,said fluid communication assembly further includes an extraction fluid sensor assembly positioned proximate said collection vial, said sensor assembly being operable to sense at least one of the presence of said collection vial and a level of said extraction fluid in said collection vial, said extraction fluid sensor assembly being operatively coupled to said controller for communication of sensor signals thereto, and said controller being responsive to said sensor signals to control the flow of said extraction fluid to said cell.
 32. The apparatus as defined in claim 31 wherein,said extraction fluid sensor assembly is operable to sense a plurality of levels of said extraction fluid in said collection vial.
 33. The apparatus as defined in claim 32 wherein,said extraction fluid sensor assembly is comprised of a plurality of optical sensors positioned to sense the level of said extraction fluid in said collection vial by passing an optical beam through said collection vial; and said collection vial is sufficiently transparent to said optical beam for sensing through said collector vial.
 34. The apparatus as defined in claim 29 wherein,said collection manipulation assembly simultaneously moves said outlet conduit and said vent conduit into substantially sealed relation with said selected one of said collection vials in said extended position.
 35. The apparatus as defined in claim 27 wherein,said collection manipulation assembly further carries said outlet conduit of said fluid communication assembly, and said collection manipulation assembly is operable for movement of said outlet conduit between a retracted position, out of fluid communication with said collection vials, and an extended position at which said outlet conduit is positioned for flow of said extraction fluid into a selected one of said collection vials while mounted in said movable vial rack.
 36. The apparatus as defined in claim 1 wherein,said fluid communication assembly further includes a flushing assembly fluidly coupled for selective flow of a flushing fluid to said inlet conduit and said cavity, said flushing assembly including a source of flushing fluid and a valve assembly operably connected to said controller for movement of said valve assembly to produce selective flow of a flushing fluid to said cavity.
 37. The apparatus as defined in claim 36 wherein,,said source of flushing fluid is provided by a reservoir of a gas under pressure.
 38. The apparatus as defined in claim wherein,said fluid communication assembly includes a rinsing assembly fluidly coupled for selective flow of a rinsing fluid to said cavity and to said outlet conduit and operatively coupled to said controller.
 39. The apparatus as defined in claim 1 wherein,said fluid communication assembly includes a pneumatic flow control manifold operatively coupled to said controller and provided with a plurality of solenoid-actuated valves operated by said controller and positioned to control fluid flow in said apparatus.
 40. The apparatus as defined in claim 1 wherein,said controller is electrically powered and includes a user input, and a memory device having a sequence establishing program stored therein, said memory device further being programmable by said user input to change said sequence establishing program.
 41. The apparatus as defined in claim 1, anda fluid collection cell having a central cavity dimensioned for receipt of a sample therein, said collection cell further being formed with at least one passageway structure communicating with said central cavity, and said collection cell being mounted in said tray.
 42. The apparatus as defined in claim 41 wherein,said collection cell includes at least one removable cap member providing access to said central cavity for placement of said sample in said central cavity.
 43. The apparatus as defined in claim 42 wherein,said collection cell includes a cap seal assembly constructed and arranged for sealing said cap by application of an inwardly directed force to said cap.
 44. The apparatus as defined in claim 43 wherein,said cap member is threadably secured to said collection cell and provides a finger-tight structure for applying said force to said cap seal assembly.
 45. The apparatus as defined in claim 44 wherein,said cell manipulating assembly is operable to grip said collection cell by said inlet conduit and said outlet conduit between said cap member and an opposed surface to apply an additional inwardly directed force to said cap member to augment sealing of said cap member.
 46. The apparatus as defined in claim 45 wherein,said oven assembly includes a clamping structure operable to clamp said collection cell therein between said cap member and an opposed surface to apply still another additional inwardly directed force to said cap member.
 47. The apparatus as defined in claim 41 wherein,said collection cell is further formed with a passageway sealing assembly formed for sealing of said inlet conduit and said outlet conduit to said passageway structure.
 48. The apparatus as defined in claim 47 wherein,said collection cell has an elongated hollow body and removable end caps mounted to said body to define said central cavity, said collection cell further has inlet passageway in one end cap and an outlet passageway in the other end cap, and collection said cell has a pair of cap seal assemblies sealing each of said end caps to said body upon application of a sealing force thereto, and a pair of passageway sealing assemblies sealing positioned for sealing inlet conduit and said outlet conduit to said collection cell.
 49. The apparatus as defined in claim 1 wherein,said inlet conduit and said outlet conduit are constructed and arranged to cooperate with surfaces on said cell to produce alignment of said cell with said inlet conduit and said outlet conduit as said cell manipulation assembly moves said inlet conduit and said outlet conduit into engagement with said cell.
 50. The apparatus as defined in claim 49 wherein,said inlet conduit and said outlet conduit are each formed with tapered alignment surfaces which cooperate with mating surfaces on said cell.
 51. The apparatus as defined in claim 50 wherein,said tapered surfaces are frusto-conical.
 52. The apparatus as defined in claim 50 wherein,said tapered surfaces are constructed and arranged to cooperate with mating surfaces on said cell to stabilize said cell as gripped between said inlet conduit and said outlet conduit.
 53. An apparatus for extraction of an analyte from a sample comprising:a cell support structure; a sample containment cell mounted in said cell support structure and having a body defining a sample-receiving cavity, a removable cap mounted to said cell over an access opening in said body to said cavity for positioning a sample therein, a passageway extending through said cap to said cavity for the flow of an extraction fluid through said cap, a cap seal assembly positioned between said body and said cap to seal said cap to said body upon application of an inward force to said cap, and a passageway sealing assembly carried by said cell proximate said passageway; a fluid communication assembly mounted proximate said cell support structure and being operable for selective fluid coupling to and uncoupling from said fluid passageway for communication of an extraction fluid to and from said cavity, said fluid communication assembly further being operable to produce an elevated pressure of said extraction fluid in said cavity; and a manipulation assembly mounted proximate said cell support structure and operable to move a portion of said fluid communication assembly into sealed relation with said passageway sealing assembly carried by said cell for fluid coupling of said fluid communication assembly to said passageway; an oven assembly mounted proximate said, cell support structure, said manipulation assembly being operable to move said cell between said cell support structure and said oven assembly with said cell being fluidly coupled to said fluid communication assembly; and comprisinga controller coupled to said manipulation assembly and said fluid communication assembly for automatic control of the movement of fluid communication assembly into and out of fluid coupling with said cell, for control of the flow of extraction fluid to and from said sample in said cavity, and for control of pressurization of said extraction fluid in said cavity. 